JP2006036128A - Belt shape member and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which can equalize the tensional forces applied on belt cords wound before vulcanization. <P>SOLUTION: A belt shape member 10 is composed of a plurality of belt cords 11a to 11g stretched and arranged, and forms reinforcing layers of the pneumatic tire by spirally winding the respective belt cords 11a to 11g so as to be arranged almost in the peripheral direction. A plurality of the belt cords 11a to 11g have the elongation property having a rapture elongation of at least 3%. The initial stiffness of at least the belt cords 11b, 11c to be arranged at both ends of a belt shape member 10 is lower than the initial stiffness of the belt cord 11a to be arranged at the central portion of the belt shape member 10. By this configuration, the tensional forces applied on the respective belt cords 11a to 11g forming the reinforcing layers of the pneumatic tire after vulcanization are equalized by winding the belt shape member 10 on the pneumatic tire before vulcanization. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a belt-shaped member and a pneumatic tire, and more particularly to a belt-shaped member constituted by two or more belt cords having different initial stiffnesses and a pneumatic tire having a reinforcing layer formed by the belt-shaped member. .

  Generally, in a pneumatic tire mounted on a vehicle, a belt layer is provided on the outer side in the tire radial direction of the carcass layer. This belt layer is formed of a plurality of layers, and each layer is constituted by a belt-shaped member obtained by covering a plurality of aligned belt cords with a rubber member. Each layer is wide and is formed by winding one strip-shaped member one turn in the tire circumferential direction on the outer side in the tire radial direction of the carcass layer and connecting both ends of the strip-shaped member. Further, the belt layer includes a plurality of belt cords constituting a belt-like member forming a belt-like member in which a plurality of belt cords constituting the belt-like member forming any one of the layers constituting the belt layer are formed. It is formed by stacking so as to intersect. Generally, the rigidity of the pneumatic tire in the tire circumferential direction is ensured by this belt layer. However, depending on the type and shape of the pneumatic tire, the rigidity in the tire circumferential direction may not be ensured with only this belt layer. For example, in a pneumatic tire mounted on a heavy load vehicle such as a truck or a bus, a high load is applied. Therefore, it is necessary to increase the rigidity in the tire circumferential direction. There are cases where it cannot be secured. Therefore, in a conventional pneumatic tire, a reinforcing layer for reinforcing rigidity in the tire circumferential direction is provided in addition to the belt layer.

  This reinforcing layer is provided between the belt layer and the surface of the tread portion or between the belt layer and the carcass layer. The reinforcing layer is composed of one belt cord or a belt-like member obtained by covering a plurality of belt cords arranged in the same manner as the belt layer with a rubber member. Here, the reinforcing layer is formed by winding one belt cord or at least one narrow belt-like member spirally in the tire circumferential direction so that the belt cord is arranged substantially in the tire circumferential direction. The both ends of the are formed without being connected. When a reinforcing layer is formed using one belt cord, it takes a long time to form the reinforcing layer, the productivity is inferior, and it is difficult to ensure the accuracy of winding. In general, a belt-like member composed of a belt cord is used (see Patent Document 1).

JP 2003-312209 A

  By the way, when molding a pneumatic tire, vulcanization is performed and a tread pattern is formed on the surface of the tread portion by a mold. This vulcanization is performed by applying pressure to the pneumatic tire before vulcanization and applying pressure, that is, applying a lift. The pneumatic tire before vulcanization to which heat is applied by applying the lift is pushed outward in the tire radial direction. Here, since the volume change of the pneumatic tire before and after vulcanization does not occur, the pneumatic tire after vulcanization shrinks in the tire width direction compared to the pneumatic tire before vulcanization. Become. Accordingly, the plurality of belt cords constituting the belt-shaped member of the pneumatic tire formed by vulcanization move outward in the tire radial direction with respect to the center in the tire radial direction as compared to before vulcanization, and each The distance between the belt cords is narrowed.

  The plurality of belt cords constituting the belt-like member after vulcanization, that is, after the lift, are preferably flat in the tire width direction, and the intervals between the belt cords are equal. That is, it is preferable that unevenness does not occur in the reinforcing layer of the vulcanized pneumatic tire. This is because when the unevenness occurs in the reinforcing layer, the height of the rubber member interposed between the reinforcing layer and the surface of the tread changes due to the unevenness, the rigidity of the tread becomes uneven, and various performances of the pneumatic tire This is because, for example, it may cause deterioration in uneven wear resistance, noise resistance and the like. The unevenness of the reinforcing layer is caused by uneven tension acting on each belt cord wound before vulcanization, that is, before lifting.

  Here, the plurality of belt cords constituting the belt-shaped member have an elongation characteristic that easily stretches in the tire circumferential direction when moving outward in the tire radial direction with respect to the center in the tire radial direction during vulcanization, that is, during lift. Therefore, an initial stiffness lower than the stiffness of the plurality of belt cords after vulcanization is set. This initial stiffness is usually set to the same initial stiffness for all of the plurality of belt cords constituting the belt-like member.

  However, in order to wind the belt-like member in a spiral shape substantially in the tire circumferential direction, a slight angle change is required after the first turn from the start of winding due to the width of the belt-like member. Therefore, there is a risk of meandering when the belt-like member is continuously wound. When the belt-like member is spirally wound in the tire circumferential direction while meandering, it acts on the belt cords arranged at both ends of the belt-like member rather than the tension acting on the belt cord arranged at the central portion of the belt-like member. There is a possibility that the tension to be partially increased. As a result, there is a possibility that the tension acting on each belt cord wound before vulcanization, that is, before lifting, may become uneven.

  Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire capable of achieving uniform tension acting on each belt cord wound before vulcanization. It is.

  In order to solve the above-described problems and achieve the object, in the present invention, the belt cord is formed of a plurality of aligned belt cords, and the belt cords are spirally arranged so as to be substantially arranged in the tire circumferential direction. In the belt-shaped member that forms a reinforcing layer of a pneumatic tire by winding, the plurality of belt cords have an elongation characteristic of breaking elongation of 3% or more, and are disposed at least at both ends of the belt-shaped member The initial stiffness of the belt-like member is lower than the initial stiffness of the belt cord disposed at the center of the belt-like member.

  Further, in the present invention, in the pneumatic tire having a reinforcing layer that reinforces rigidity in the tire circumferential direction, the reinforcing layer is formed by spirally winding a belt-like member in the tire circumferential direction, and the belt-like member is It is composed of a plurality of belt cords having an elongation characteristic with a stretched breaking elongation of 3% or more, and at least the initial rigidity of the belt cords arranged at both ends of the belt-like member is at the center of the belt-like member. It is characterized by being lower than the initial rigidity of the belt cord to be arranged.

  According to these inventions, the initial stiffness of the belt cords arranged at both ends of the belt-like member is lower than the initial stiffness of the belt cords arranged at the central portion of the belt-like member. In other words, the belts are arranged at both ends when spirally wound in the tire circumferential direction before vulcanization and when lifted during vulcanization and moved outward in the tire radial direction with respect to the center in the tire radial direction. The cord has an elongation characteristic that is easier to stretch than the belt cord disposed in the central portion. Therefore, even if meandering occurs when the belt-like member is spirally wound in the tire circumferential direction, the belt-like member is arranged at both ends of the belt-like member rather than the tension acting on the belt cord arranged at the center of the belt-like member. An increase in the tension acting on the belt cord is suppressed, and the difference in tension acting on each belt cord constituting the belt-like member can be reduced. Thereby, it is possible to make the tension acting on each belt cord constituting the belt-shaped member wound before vulcanization uniform. The substantially tire circumferential direction refers to a range of ± 5 ° with respect to the tire equator plane when the tire equator plane is 0 °. The initial rigidity means the rigidity of the belt cord when the pneumatic tire is vulcanized, that is, when the belt cord extends from before vulcanization to after vulcanization, and the belt in the pneumatic tire after vulcanization. It is lower than the rigidity of the cord.

  According to the present invention, in the belt-shaped member, the plurality of belt cords have an initial rigidity of a belt cord disposed on an end side of the belt-shaped member among adjacent belt cords on a central portion side of the belt-shaped member. It is characterized by being below the initial rigidity of the belt cord to be arranged.

  According to the present invention, in the pneumatic tire, the plurality of belt cords are arranged such that an initial rigidity of a belt cord disposed on an end side of the belt-like member among adjacent belt cords is a central portion side of the belt-like member. The initial rigidity of the belt cord disposed on the belt cord is equal to or less than the initial rigidity.

  According to the present invention, in the belt-shaped member in which one or more belt cords are disposed between the belt cord disposed in the central portion of the belt-shaped member and the belt cord disposed in both ends of the belt-shaped member, From the end toward the both ends, the initial rigidity of the belt cord decreases gradually or stepwise. Therefore, the tension acting on the belt cords arranged on both end sides of the central portion is suppressed from being higher than the tension acting on the belt cords arranged in the central portion of the belt-like member, and the belt-like member is configured. Thus, the difference in tension acting on each belt cord can be further reduced. Thereby, it is possible to further equalize the tension acting on each belt cord constituting the belt-like member wound before vulcanization.

  In the pneumatic tire according to the present invention, the reinforcing layer is formed by spirally winding the band-shaped members without overlapping each other.

  When the belt-like members are overlapped and wound spirally, a part of the belt-like member rides on a part of the belt-like member that has already been wound, and the tension acting on the belt cord arranged on the part of the belt-like member that has run is not running There is a possibility that the tension is higher than the tension acting on the belt cord disposed in the portion. However, according to the present invention, the reinforcing layer is formed by spirally winding the band-shaped members so that it does not overlap with the reinforcing layer formed by spirally winding the band-shaped members. Since there are few portions that run on a part of the belt-like member on which a part of the belt-like member has already been wound, the tension acting on each belt cord wound before vulcanization can be made uniform.

  Since the belt-like member and the pneumatic tire according to the present invention can achieve uniform tension acting on each belt cord wound before vulcanization, the unevenness of the reinforcing layer formed by the belt-like member at least after vulcanization The effect that generation | occurrence | production of can be suppressed is produced.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following examples. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same. In the following examples, heavy-duty pneumatic tires mounted on trucks, buses, etc. will be described as pneumatic tires, but the present invention is not limited to this, and pneumatic tires mounted on passenger cars and the like are described. It may be used.

  FIG. 1 is a diagram showing a configuration example of a belt-like member according to the present invention. FIG. 2 is a diagram showing the initial rigidity of each belt cord of the belt-shaped member. FIGS. 3A and 3B are diagrams illustrating the relationship between stress and strain of each belt cord. As shown in FIG. 1, a belt-like member (belt ply) 10 forming a reinforcing layer 13 described later includes a plurality of belt cords 11a to 11g (seven in the figure) and a plurality of belt cords 11a to 11a. and a rubber member 12 covering g. The belt cords 11a to 11g are aligned so that the belt cords 11a to 11g are equally spaced at a distance W1, and are covered with a rubber member 12 (see FIG. 5). In addition, the strip | belt-shaped member 10 should just be comprised by 3 or more arrange | positioned at the center part and both ends of the strip | belt-shaped member 10, and is not comprised by seven like the strip | belt-shaped member 10 shown in FIG. Also good.

  As shown in FIG. 2, the initial rigidity of the belt cords 11 a to 11 g constituting the belt-like member 10 is determined from the belt cord 10 a arranged in the center of the belt-like member 10 in the width direction, that is, the short-side direction of the belt-like member. It becomes gradually lower toward the belt cords 10b and 10c arranged at both ends. That is, the belt-like member 10 is configured by covering the rubber member 12 with two or more belt cords having different initial rigidity. Specifically, a belt cord 11a having a high initial rigidity is disposed at the center of the belt-like member 10, and belt cords 11b and 11c having an initial stiffness lower than that of the belt cord 11a are provided at both ends of the belt-like member 10. Is arranged.

  In addition, the initial rigidity of the belt cords 11d and 11e on the center side of the belt-like member 10 disposed between the belt cord a and the belt cords 11b and 11c is lower than the initial rigidity of the belt cord 11a. It is higher than the initial rigidity of the belt cords 11f and 11g on both end sides of the belt-like member 10 disposed between the belt cords 11b and 11c. Further, the initial stiffness of the belt cords 11f and 11g on both ends of the belt-like member 10 disposed between the belt cord a and the belt cords 11b and 11c is lower than the initial stiffness of the belt cords 11d and 11e. It is higher than the initial rigidity of 11b and 11c. That is, the initial rigidity of the belt cords 11d to 11g disposed between the belt cord a disposed at the center of the belt-shaped member 10 and the belt cords 11b and 11c disposed at both ends is determined by the belt cords 11d to 11g. Is lower than the initial rigidity of the belt cords 10a, 11d, and 11e on the center side of the belt-like member 10 adjacent to the belt member 10. Accordingly, the initial rigidity of the plurality of belt cords 11a to 11g constituting the belt-like member 10 is in the relationship of belt cord 11a> belt cords 11d, 11e> belt cords 11f, 11g> belt cords 11b, 11c.

  The belt cords 11a to 11g constituting the belt-shaped member 10 have a stepwise decrease in initial rigidity from the center portion in the width direction of the belt-shaped member 10, that is, from the center portion to the both ends in the short-side direction of the belt-shaped member 10. May be. Specifically, for example, the initial stiffness of the belt cords 11d and 11e arranged in the vicinity of the central portion of the belt-like member 10 is set to be equal to the initial stiffness of the belt cord 11a arranged in the central portion and / or the belt-like member 10 The initial stiffness of the belt cords 11f and 11g disposed near both ends of the belt may be the same as the initial stiffness of the belt cords 11b and 11c disposed at both ends.

  Each belt cord 11a-g is comprised by twisting several strands. Here, the strand is made of, for example, a fiber such as nylon fiber, rayon fiber, polyester fiber, aramid fiber, carbon fiber, or steel. The initial rigidity of each of the belt cords 11a to 11g can be varied depending on the twisting strength of the plurality of strands. Specifically, the thickness of the plurality of strands is constant, and if the twist is tightened, the initial rigidity of each belt cord 11a-g is lowered, and if the twist is loosened, the initial rigidity of each belt cord 11a-g is increased. Become. Accordingly, the strands of the plurality of strands constituting the belt cords 11a to 11g constituting the belt-like member 10 are gradually moved from the belt cord 10a arranged at the central portion toward the belt cords 10b and 10c arranged at both ends. Alternatively, by tightening in stages, the initial rigidity of the belt cords 11a to 11g decreases from the belt cord 10a arranged at the center toward the belt cords 10b and 10c arranged at both ends.

  Moreover, the initial rigidity of each belt cord 11a-g is set so that it may become lower than the rigidity of each belt cord 11a-g in the pneumatic tire 1 after vulcanization. Here, the initial stiffness of each belt cord 11a-g is set based on the relationship between stress and strain. For example, as shown in FIG. 3A, the belt cords 11a to 11g are changed by making the stresses (Y1 to 4) of the belt cords 11a to 11g necessary for generating a strain equal to or less than a predetermined strain X to be different. Set the initial stiffness of. Specifically, since a strain equal to or less than a predetermined strain X occurs, the stress Y4 that requires the belt cord a (dotted line in the figure) and the stress Y3 that requires the belt cords 11d and 11e (dotted line in the figure) The belt cords 11f and 11g are set so as to decrease in the order of necessary stress Y2 (two-dot chain line in the figure) and belt cords 11b and 11c in the order of necessary stress Y1 (solid line in the figure). That is, the belt cords 11a to 11g are set so that the distortion of the belt cords 11a to 11g decreases with respect to the stress from the belt cord 10a disposed at the center toward the belt cords 10b and 10c disposed at both ends.

  Alternatively, as shown in FIG. 3-2, the belt cords 11 a to 11 g are made different from each other by changing the distortion (X 1 to 4) generated in the belt cords 11 a to 11 g by applying a stress equal to or lower than a predetermined stress Y. Set the initial stiffness. Specifically, by applying a stress equal to or lower than a predetermined stress Y, a strain X1 (solid line in the figure) generated in the belt cord a, and a strain X2 generated in the belt cords 11d and 11e (two-dot chain line in the drawing). The distortion X3 (indicated by the alternate long and short dash line in the figure) generated in the belt cords 11f and 11g and the distortion X4 (indicated by the dotted line in the figure) generated in the belt cords 11b and 11c are set to increase in this order. That is, the stress of the belt cords 11a to 11g is set so as to become sharper with respect to the distortion from the belt cord 10a disposed at the central portion toward the belt cords 10b and 10c disposed at both ends.

  Moreover, each belt cord 11a-g has the elongation characteristic whose breaking elongation is 3% or more. Here, the elongation characteristic with a breaking elongation of 3% or more means that the belt cord without tension is not stretched unless it is stretched by 3% or more with respect to the length of the belt cord without tension. It is a characteristic.

  Next, the pneumatic tire 1 having the reinforcing layer 13 formed by the belt-like member 10 according to the present invention will be described. FIG. 4 is a view showing a configuration example of a pneumatic tire using the belt-like member according to the present invention. 1 is a partial cross-sectional view of a cross section of the pneumatic tire 1 taken along the meridian plane. As shown in FIG. 1, the pneumatic tire 1 includes a tread portion 2, a sidewall portion 3, and a tire bead portion 4. The tread portion 2 includes at least an inner liner 5, a carcass layer 6 laminated on the inner liner 5, and a belt layer 7 laminated on the carcass layer 6. The sidewall portion 3 includes an inner liner 5, a carcass layer 6 laminated on the inner liner, and a side tread (not shown). The tire bead portion 3 includes at least a bead core 8 made of a plurality of steel wires for mounting the pneumatic tire 1 on a rim (not shown) and a bead filler 9. In the pneumatic tire 1 formed by vulcanization, a plurality of land portions 22 defined by the groove portions 21 are formed on the surface of the tread portion 2.

  The belt layer 7 is for securing rigidity in the tire circumferential direction, and is composed of a plurality of layers. However, when the rigidity in the tire circumferential direction cannot be ensured by the belt layer 7 alone, it is shown in FIG. As described above, the pneumatic tire 1 has the reinforcing layer 13 laminated on the belt layer 7. The reinforcing layer 13 is formed by a single belt-like member 10, and each belt cord 11a to 11g is substantially in the tire circumferential direction, that is, when the tire equatorial plane is 0 °, The belt cords 11a to 11g are arranged to be inclined within a range of ± 5 °.

  A method for forming the reinforcing layer 13 of the pneumatic tire 1 using the belt-like member 10 according to the present invention will be described. FIG. 5 is a cross-sectional view of a main part of the pneumatic tire 1 before vulcanization. FIG. 6 is a view showing tension acting on each belt cord of the belt-like member before vulcanization. FIG. 7 is a view showing a cross-sectional view of a main part of a pneumatic tire 1 using a conventional band member after vulcanization. FIG. 8 is a cross-sectional view of the main part of the pneumatic tire 1 in which the band-shaped member according to the present invention after vulcanization is used.

  The method for forming the reinforcing layer 13 of the pneumatic tire 1 by the belt-like member 10 includes a step of winding the belt-like member 10 in the pneumatic tire 1 before vulcanization and a step of forming the pneumatic tire 1 by vulcanization. In the step of winding the belt-shaped member 10, first, the belt-shaped member 10 is wound around the outer side of the belt layer 7 in the tire radial direction by one turn in the tire circumferential direction. Next, the belt-shaped member 10 wound for one turn is wound spirally around the outer side in the tire radial direction of the belt layer 7 without overlapping with the already wound portion of the belt-shaped member 10, that is, without wrapping. At this time, when the belt-like member 10 is substantially in the tire circumferential direction, that is, when the tire equatorial plane is set to 0 °, the belt-like member 10 (each belt cord 11a to g) is within a range of ± 5 ° with respect to the tire equatorial plane. It is wound in the direction of inclination. And the strip | belt-shaped member 10 wound by multiple turns helically is wound by 1 turn in a tire circumferential direction. Thereby, the process of winding the strip | belt-shaped member 10 in the pneumatic tire 1 before vulcanization is complete | finished. As shown in FIG. 5, the belt-like member 10 in the pneumatic tire 1 before vulcanization does not overlap in a cross section cut by a meridian plane of the pneumatic tire 1 before vulcanization, that is, a cross section in the tire width direction.

  At this time, when the belt-like member 10 is continuously spirally wound around the outer side in the tire radial direction of the belt layer 7, the belt-like member 10 may be wound while meandering in the tire width direction. When the belt-like member 10 is wound while meandering, a portion that is pulled from the central portion and a portion that is not pulled from the central portion are generated at both ends of the belt-like member 10. Therefore, the belt cords 11b and 11c arranged at both ends of the belt-like member 10 are partly pulled more than the belt cord 11a arranged at the central portion. For example, in the conventional belt-like member 100 constituted by a plurality of belt cords 101a to 101g having the same initial rigidity, the belt cord 101a disposed at the center of the conventional belt-like member 100 as shown in FIG. The tension acting on the belt cords 101b and 101c arranged at both ends may be higher than the tension acting on the belt. In addition, the tension acting on the belt cords 101d to 101g arranged between the belt cord 101a and the belt cords 101b and 101c is also gradually increased from the central portion of the conventional belt-shaped member toward both ends pulled from the central portion. Can be expensive. That is, when a conventional belt-shaped member composed of a plurality of belt cords 101a to 101g having the same initial rigidity is wound while meandering, the tension acting on each belt cord 101a to 101g is arranged at the center of the conventional belt-shaped member. The belt cord 101a may gradually become higher toward the belt cords 101b and 101c disposed at both ends thereof.

  However, in the belt-like member 10 according to the present invention, the initial rigidity of the belt cords 11b and 11c arranged at both ends is lower than the initial rigidity of the belt cord 11a arranged at the center, that is, the belt arranged at both ends. The cords 11b and 11c are easier to extend than the belt cord 11a disposed at the center. Therefore, as shown in FIG. 6, it is possible to suppress the tension acting on the belt cords 11b and 11c arranged at both ends from becoming higher than the tension acting on the belt cord 11a arranged at the center of the belt-like member 10. be able to. That is, as shown to A of the figure, compared with the tension | tensile_strength which acts on the belt cords 11b and 11c arrange | positioned at the both ends of the conventional strip | belt-shaped member shown to C of the figure, of the strip | belt-shaped member 10 concerning this invention The tension acting on the belt cords 11b and 11c arranged at both ends is reduced. Further, the tension acting on the belt cords 11d to 11g arranged between the belt cord 11a and the belt cords 11b and 11c is larger than the central portion of the belt-like member 10 from the central portion as compared with the conventional belt-like member. It is suppressed that it becomes high gradually toward the both ends pulled. That is, even if the belt-like member 10 according to the present invention is wound while meandering, the belt cords 11b and 11c arranged at both ends of the belt cord 11a arranged at the central portion of the belt-like member 10 and the both ends are arranged. It is suppressed that the tension acting on the belt cords 11d to g arranged on the portion side is increased, and the difference in tension acting on the belt cords 11a to 11g constituting the belt-like member 10 is determined for each of the belt-like members constituting the conventional belt-like member. The difference in tension acting on the belt cords 100a to 100g can be made smaller. Thereby, the tension acting on the belt cords 11a to 11g constituting the belt-like member 10 can be made uniform.

  Further, as shown in FIG. 5, the band-shaped member 10 according to the present invention is spirally wound in a substantially circumferential direction without overlapping, so a part of the band-shaped member 10 in which a part of the band-shaped member 10 has already been wound is provided. Never ride on. Therefore, like the conventional belt-like member 100, a part of the belt-like member 100 rides on, and is arranged on a portion where the tension acting on the belt cords 101a to 101g arranged on the belt-like member 100 is not run. Since it can suppress becoming higher than the tension | tensile_strength which acts on a belt cord, the tension | tensile_strength which acts on each belt cord 10a-g wound before vulcanization can be aimed at.

  Further, even if the belt-like member 10 is wound while meandering, both ends of the belt-like member 10 are easier to move than the central portion, that is, excessive tension does not act on the belt cords 11b and 11c arranged at both ends. The band-shaped member 10 can be easily wound.

  Next, the process of shape | molding the pneumatic tire 1 by vulcanization | cure of the formation method of the reinforcement layer 13 of the pneumatic tire 1 by the strip | belt-shaped member 10 is demonstrated. A pneumatic tire 1 (green tire) before vulcanization in which a carcass layer 5, a belt layer 7, a reinforcing layer 13, and the like are laminated and a tread portion 2 is formed is placed on a mold (not shown) heated by a heating device (not shown). By being mounted and pressurized by a pressure device (not shown), that is, by applying a lift, it moves while deforming outward in the tire radial direction with respect to the center in the tire radial direction (not shown).

  Since the volume change of the pneumatic tire 1 during vulcanization does not occur before and after vulcanization, when the lift is applied, the pneumatic tire 1 contracts in the tire width direction as compared with the pneumatic tire 1 before vulcanization. Thereby, the reinforcement layer 13 is formed by winding the strip | belt-shaped member 10 spirally in a tire peripheral direction substantially. In the vulcanized pneumatic tire 1 after vulcanization, as shown in FIGS. 7 and 8, a tread pattern formed on a mold (not shown) is transferred to the surface of the tread portion 2 of the pneumatic tire 1. A tread pattern, that is, a land portion 22 partitioned by a predetermined groove portion 21 is formed on the surface of the tread portion 2.

  At this time, since the pneumatic tire 1 at the time of vulcanization moves while deforming outward in the tire radial direction, the plurality of belt cords 11a to 11g constituting the wound belt-like member 10 are centered in the tire radial direction. On the other hand, a force in the tire radial direction that moves outward in the tire radial direction acts. The force in the tire radial direction acts on each belt cord 11a-g as a force pulling each belt cord 11a-g. Further, since the pneumatic tire 1 at the time of vulcanization is contracted in the tire width direction, the plurality of belt cords 11a to 11g constituting the wound belt-shaped member 10 are directed from both end portions of the belt-shaped member 10 toward the central portion. Therefore, the force in the tire width direction acts.

  Here, as shown in FIG. 7, when the belt-like member 100 constituted by a plurality of belt cords 101a to 101g having the same initial stiffness is wound, the belt cord 101a disposed at the center thereof is wound around the belt cord 101a. The tension acting on the belt cords 101b and 101c arranged at both ends is higher than the acting tension. That is, both ends of the conventional belt-shaped member 100 are strongly pressed against the belt layer 7, and the belt cords 101 b and 101 c disposed at both ends are more than the belt cord 101 a disposed at the center. It is difficult to move outward in the tire radial direction with respect to the center in the tire radial direction, that is, the restriction of the conventional belt-shaped member 100 is strongly received. However, the belt cord 101a disposed at the central portion of the conventional belt-shaped member 100 is more easily moved outward in the tire radial direction than the belt cords 101b and 101c disposed at both ends thereof. . Therefore, when a force in the tire radial direction and a force in the tire width direction are applied to the conventional belt-shaped member 100, the belt cords 101b and 101c move so as to enter the central portion of the belt-shaped member 100, and the belt cords 101b and 101c cause the belt to move. The cord 101a is pushed outward in the tire radial direction, and the conventional belt-shaped member 100 may have a convex cross-sectional shape in the width direction. As a result, the plurality of belt cords 101 a to 101 g constituting the conventional belt-shaped member 100 are not flat in the tire width direction, and the interval between the belt cords 101 a to 101 g is particularly adjacent to the conventional belt-shaped member 100. There is a possibility that the interval W3 between the belts 101b and 101c arranged at the matching ends is larger than the interval between the other belt cords 101a to 101g, and the reinforcing layer 13 formed by this conventional belt-like member 100 has irregularities. There was a risk of occurrence.

  However, as shown in FIG. 8, even when the belt-like member 10 according to the present invention is wound, it acts on the belt cords 11b and 11c arranged on both ends and the tension acting on the belt cord 11a arranged at the center portion thereof. It is suppressed that the difference from the tension to be increased is higher than that of the conventional belt-shaped member 100. That is, the belt-like member 10 according to the present invention is restrained from being strongly pressure-bonded at both ends thereof to the belt layer 7, and the belt cords 11 b and 11 c arranged at both ends are tires with respect to the center in the tire radial direction. It is easy to move outward in the radial direction, that is, it is difficult to be restricted by the belt-like member 10. Accordingly, when a force in the tire radial direction and a force in the tire width direction are applied to the belt-shaped member 10 according to the present invention, the plurality of belt cords 11a to 11g constituting the belt-shaped member 10 are tires as shown in FIG. It becomes flat in the width direction, and the intervals W2 between the belt cords 101a to 101g are equal to each other, and it is possible to suppress the occurrence of irregularities in the reinforcing layer 13 formed by the belt-shaped member 10. Thereby, the change by the unevenness | corrugation of the height of the rubber member interposed between the reinforcement layer 13 and the surface of the tread part 2 can be suppressed, the rigidity of the tread part 2 can be made uniform, and various performances of the pneumatic tire can be achieved. For example, deterioration of uneven wear resistance, noise resistance and the like can be suppressed.

  Further, after vulcanization, that is, the tension acting on the plurality of belt cords 11a to 11g arranged substantially in the tire circumferential direction constituting the reinforcing layer 13 of the molded pneumatic tire 1 is approximately the tire circumference before vulcanization. Since the tension acting on the belt cords 11a to 11g constituting the belt-like member 10 wound spirally in the direction can be made uniform, it acts uniformly. Therefore, since there is no belt cord 11a-g to which tension acts excessively, durability of each belt cord 11a-g can be improved.

  In addition, in the said Example, although the reinforcement layer 13 is arrange | positioned at the tire radial direction outer side of the belt layer 7, it is not limited to this, Between the belt layer 13 and the carcass layer 7, or a carcass layer 7 and the inner liner 5 may be arranged. Further, in the above embodiment, the reinforcing layer 13 is formed by the single belt-like member 10, but the present invention is not limited to this, and the two or more belt-like members 10 are spirally formed without substantially overlapping in the tire circumferential direction. You may form by winding in the shape. Moreover, in the said Example, although the reinforcement layer 13 was comprised by the single layer, you may comprise by laminating | stacking a some layer. In this case, since the tension acting on the belt cords 11a to 11g arranged in each layer can be made uniform, it is possible to suppress the occurrence of unevenness in the reinforcing layer 13 composed of a plurality of layers.

  Moreover, in the said Example, although the strip | belt-shaped member 10 is not overlapped, the reinforcement layer 13 is formed by spirally winding in a tire circumferential direction substantially, but you may overlap. In this case, a part of the belt-like member 10 rides on a part of the belt-like member 10 that has already been wound. However, in the belt-like member 10 according to the present invention, the belt disposed on the part of the belt-like member 10 that rides on the belt. It is possible to suppress an increase in the difference between the tension acting on the cord and the tension acting on the belt cord disposed on the portion not running on the cord. Therefore, since the tension acting on each belt cord wound before vulcanization can be made uniform, the belt cord disposed on the overlapping portion of the belt-like member 10 after vulcanization and the portion that rides on the belt cord It can suppress that the space | interval between the belt cords arrange | positioned in is excessively narrow. Thereby, when the pneumatic tire 1 rolls, it can suppress that this belt cord mutually rubs, and the durability of a belt cord can be improved.

  Further, the initial rigidity of each belt cord 11a to 11g may be varied by changing the thickness of a plurality of strands (not shown) with a constant twist strength. Specifically, if the strands are thick, the initial stiffness of each belt cord 11a-g is high, and if the strands are thin, the initial stiffness of each belt cord 11a-g is low. Therefore, the belt cords 10b arranged at both ends from the belt cord 10a arranged at the center to the thickness of the plurality of strands constituting the belt cords 11a to 11g arranged on the rubber member 12 of the belt-like member 10 are used. , 10c may be reduced gradually or stepwise.

  As described above, the belt-like member and the pneumatic tire according to the present invention are useful for a pneumatic tire having a belt-like member and a reinforcing layer that form a reinforcing layer for securing rigidity in the tire circumferential direction. It is suitable for equalizing the tension acting on each belt cord wound before vulcanization.

It is a figure which shows the structural example of the strip | belt-shaped member concerning this invention. It is a figure which shows the initial stage rigidity of each belt cord of a strip | belt-shaped member. It is a figure which shows the relationship between the stress and distortion of each belt cord. It is a figure which shows the relationship between the stress and distortion of each belt cord. It is a figure which shows the structural example of the pneumatic tire using the strip | belt-shaped member concerning this invention. It is principal part sectional drawing of the pneumatic tire 1 before vulcanization. It is a figure which shows the tension | tensile_strength which acts on each belt cord of the strip | belt-shaped member before vulcanization. It is a figure which shows the principal part sectional drawing of the pneumatic tire 1 in which the conventional strip | belt-shaped member after vulcanization was used. It is a figure showing the important section sectional view of pneumatic tire 1 in which the beltlike member concerning this invention after vulcanization was used.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heavy duty pneumatic tire 2 Tread part 21 Groove part 22 Land part 3 Side wall part 4 Tire bead part 5 Inner liner 6 Carcass layer 7 Belt layer 8 Bead core 9 Bead filler 10 Belt-like member 11a-g Belt cord 12 Rubber member 13 Reinforcement layer

Claims (5)

In a belt-shaped member that is formed of a plurality of aligned belt cords and forms a reinforcing layer of a pneumatic tire by spirally winding each belt cord so that the belt cords are arranged substantially in the tire circumferential direction.
The plurality of belt cords have an elongation characteristic of breaking elongation of 3% or more,
A belt-like member, wherein an initial rigidity of a belt cord arranged at least at both ends of the belt-like member is lower than an initial rigidity of a belt cord arranged in a central portion of the belt-like member.   In the plurality of belt cords, the initial stiffness of the belt cords arranged on the end side of the belt-like member among the adjacent belt cords is equal to or lower than the initial stiffness of the belt cords arranged on the central portion side of the belt-like member. The strip-shaped member according to claim 1. In a pneumatic tire having a reinforcing layer that reinforces rigidity in the tire circumferential direction,
The reinforcing layer is formed by spirally winding a belt-like member in the tire circumferential direction,
The belt-shaped member is composed of a plurality of belt cords having an elongation characteristic such that the aligned elongation at break is 3% or more, and at least the initial rigidity of the belt cord disposed at both ends of the belt-shaped member is the belt-shaped member. A pneumatic tire characterized by being lower than the initial rigidity of a belt cord disposed in a central portion of the member.   In the plurality of belt cords, the initial stiffness of the belt cords arranged on the end side of the belt-like member among the adjacent belt cords is equal to or lower than the initial stiffness of the belt cords arranged on the central portion side of the belt-like member. The pneumatic tire according to claim 3.   The pneumatic tire according to claim 3 or 4, wherein the reinforcing layer is formed by spirally winding the band-shaped members without overlapping each other.

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